Stroke Victims Use Minds to Control Robotic Arms

Action Points

Brain control of robotic limbs appears possible, according to preliminary results in two patients with no functional arm control due to brainstem stroke.

Point out that the robotic arms also showed promise in assisting in the activities of daily living, and one of the patients was able to grab a bottle of coffee and drink through a straw.

Controlling robotic limbs with neural impulses appears possible, according to preliminary results in two patients left with no functional control of their arms after a brainstem stroke.

Using an investigational neural interface system -- called BrainGate -- the quadriplegics were able to direct robotic arms to touch and grab foam balls, according to Leigh Hochberg, MD, PhD, of Brown University in Providence, R.I., and colleagues.

And one of the patients was able to grab a bottle of coffee and drink through a straw, the researchers reported in the May 17 issue of Nature.

"Although robotic reach and grasp actions were not as fast or accurate as those of an able-bodied person, our results demonstrate the feasibility for people with [quadriplegia], years after injury to the central nervous system, to recreate useful multidimensional control of complex devices directly from a small sample of neural signals," they wrote.

"Though further developments might enable people with [quadriplegia] to achieve rapid, dexterous actions under neural control, at present, for people who have no or limited volitional movement of their own arm, even the basic reach and grasp actions demonstrated here could be substantially liberating, restoring the ability to eat and drink independently."

Hochberg and colleagues previously reported that patients with long-standing quadriplegia could use a neural interface system to move and click a computer cursor. Additional studies showed that able-bodied monkeys could use neural signals to move a robotic arm.

The BrainGate2 pilot clinical trial began enrolling patients to see whether similar results could be achieved in humans.

The researchers reported results from two participants -- S3, a 58-year-old woman, and T2, a 66-year-old man. Both lacked function in all four limbs and could not speak because of a brainstem stroke. The woman entered the study nearly 15 years after her stroke and the man entered the study 5.5 years after the event.

In both patients, a 96-channel microelectrode array was implanted in the motor cortex, which controls movement. S3 received her implant 5.3 years before the study and T2 received his 5 months before the study.

Neural signals detected by the electrodes were translated by an external computer and used to control two robotic arms -- the DLR Light-Weight Robot III, which was designed by the German Aerospace Center as an assistive device, and the DEKA Arm System, which was designed as an advanced upper limb replacement for individuals with an arm amputation.

Both patients tried to use their brain signals to move the robotic arms to grasp foam ball targets flexible supports. S3 performed 158 trials over four sessions and successfully touched the targets in 48.8% of DLR trials and 69.2% of the DEKA trials. T2, who used only the DEKA system, performed 45 trials in a single session and successfully touched the targets 95.6% of the time

Of the successful touches, S3 was able to grasp the target 43.6% and 66.7% of the time with the DLR and DEKA systems, respectively. T2 grasped the target 65.1% of the time.

The robotic arms also showed promise in assisting in the activities of daily living. In four out of six attempts, S3 used the robotic arm to grab a bottle of coffee, bring it to her mouth, drink out of a straw, and place the bottle back on the table.

"This was the first time since the participant's stroke more than 14 years earlier that she had been able to bring any drinking vessel to her mouth and drink from it solely of her own volition," the authors wrote.

"The use of neural interface systems to restore functional movement will become practical only if chronically implanted sensors function for many years," they added. "It is thus notable that S3's reach and grasp control was achieved using signals from an intracortical array implanted over 5 years earlier."

The research was supported by the Rehabilitation Research and Development Service, Office of Research and Development, Department of Veterans Affairs. Support was also provided by the National Institute of Neurological Disorders and Stroke, the Eunice Kennedy Shriver National Institute of Child Health & Human Development, the National Institute on Deafness and Other Communication Disorders, the National Center for Medical Rehabilitation Research, the National Institute of Biomedical Imaging and Bioengineering, a Memorandum of Agreement between the Defense Advanced Research Projects Agency (DARPA) and the Department of Veterans Affairs, the Doris Duke Charitable Foundation, the MGH-Deane Institute for Integrated Research on Atrial Fibrillation and Stroke, Katie Samson Foundation, Craig H. Neilsen Foundation, and the European Commission's Seventh Framework Program through the project The Hand Embodied. The pilot clinical trial into which participant S3 was recruited was sponsored in part by Cyberkinetics Neurotechnology Systems (CKI), which ceased operations in 2009.

Hochberg received research support from Massachusetts General and Spaulding Rehabilitation Hospitals, which in turn received clinical trial support from Cyberkinetics. One of his co-authors is a former chief scientific officer and a former director of CKI; he held stocks and received compensation.

Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner

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